Enhancement of toluene oxidation performance over Cu–Mn composite oxides by regulating oxygen vacancy

Abstract

Oxygen vacancy plays an important role in regulating the chemical and catalytic properties of catalysts. In this paper, Cu-Mn composite oxide catalyst was firstly synthesized by hydrothermal method and then modified by urea solid reaction treatment to obtain CM-X catalysts (X = 2, 4, 6, where × represents the weight ratio of urea/CM catalyst) with different oxygen vacancy concentrations. The relationship between the structure and catalytic performance of these catalysts was analyzed by a variety of characterization techniques. The CM-4 sample showed the maximum specific surface area, which enhanced the adsorption capacity of the catalyst to the reactants. Moreover, there existed a large number of oxygen vacancies in CM-4 samples, leading to the amount increase of adsorbed oxygen species on the surface and high migration ability of lattice oxygen, which can improve the catalyst reducibility and oxygen species activity. Therefore, the CM-4 catalyst showed the excellent catalytic activity and stability for toluene oxidation, and toluene could be completely oxidized into CO2 and H2O at 215 °C under the equivalent gas hourly space velocity (GHSV) of 22,500 mLg-1h−1. And it was found by in situ DRIFTS experiment that the oxidation of toluene occurs via the benzyl alcohol-benzoate-anhydride reaction pathway on CM-4 catalyst.